Unexpectedly high incidence of Pneumocystis carinii infection after lung-heart transplantation. Implications for lung defense and allograft survival.

Pneumonia due to Pneumocystis carinii (PCP) is regularly encountered in organ allograft recipients who are immunosuppressed to prevent rejection. Recipients of lung/heart allografts may be particularly prone to pulmonary infection due to systemic immunosuppression and the fact that defense mechanisms in the transplanted lung may be further impaired through tissue incompatibility and the effects of surgery. In this study, we monitored 16 lung transplant recipients for infection with Pneumocystis carinii using serial bronchoalveolar lavage (BAL) and found the prevalence of Pneumocystis infection of the lung to be 88%. Six episodes were associated with the usual symptoms of pneumonia, whereas 10 episodes were associated with minimal or no symptoms. In 3 of the 6 symptomatic episodes, a concurrent bacterial infection was also found. The total number of cells recovered from the lung by BAL, the proportion of T-lymphocytes, and the number of cytotoxic/suppressor and helper/inducer cells were elevated during infection with Pneumocystis compared to before and after. Spontaneous and interleukin-2-induced proliferation of BAL cells in vitro was also higher during infection, suggesting that there was an increased number of activated T-lymphocytes in the airspaces of the infected allograft. BAL cells cultured with irradiated spleen cells from the donor proliferated at higher levels when obtained after Pneumocystis infection than when obtained before or during infection even for subclinical infections. These results indicate that in the absence of prophylaxis, the prevalence of Pneumocystis infestation is very high after lung/heart transplantation. Impaired defense of the transplanted lung does not seem to stem from the inability of activated T-lymphocytes to accumulate in the allograft.(ABSTRACT TRUNCATED AT 250 WORDS)